Cable ties have been widely used for the bundling of electrical conductors. Such devices are typically formed by injection molding of a thermoplastic material to form a toothed strap having a head with an aperture therethrough for receipt of the toothed strap. A movable pawl within the head engages the toothed strap to prevent retrograde movement of the strap through the head. An example of such a cable tie is disclosed in Caveney et al. U.S. Pat. No. 3,965,538. As the length of the strap portion increases, so does the difficulty in molding such a product. In an effort to minimize the molding problems associated with long, thin parts, it has been proposed to mold a shorter strap section and stretch the section to its desired length which may be two and a half to three times the as-molded length. An example of such a cable tie is found in Paradis U.S. Pat. No. 4,754,529.
Stretching has been found to alleviate the problems associated with molding extremely long, thin parts, but the stretching process produces a new set of problems. The spacing of the strap teeth as molded is very accurate. However, once a tie has been stretched, it is very difficult to maintain uniformity of the distance between the strap teeth as a result of tolerances in the manufacturing process. Additionally, the as-molded profiles of the strap teeth will change during stretching. Furthermore, the stretching reorients the molecules which provides the desirable feature of increased strength for the same corresponding cross-section but the surface of the tie becomes very tough and promotes slippage of the strap teeth as compared to the as-molded condition.
When the commercial cable tie embodied in accordance with the disclosure of Paradis U.S. Pat. No. 4,754,529 is actually loaded under loads approaching the rated load, the teeth 22t-1 and 22t-2, as shown in FIG. 5C of the '529 patent, will disengage from the strap leaving only tooth 22t-3 on the pawl engaged with the strap. Upon applying a load to the '529 cable tie there is actually a point where the strap will undergo retrograde movement relative to the head and the strap tooth engaged with the fixed tooth 23t will disengage such that the fixed tooth 23t skips to the next strap tooth and actually changes the tension applied around a bundle. Such an event is undesirable when the cable tie is maintaining a bundle of wires or the like at a predetermined tension.